minor changes on SSGPLVM
linear kernel psi statistics performance optimization
some further performance improvement for linear kernel psi statistics
fix the pickle problem for models with psi statistics
update additive kernel for SSGPLVM
a bug fix for psi statistics related model pickle
[pickling] wb as write parameter
[linear] einsums
[ard] enhanced ard handling and plotting

Conflicts:
	GPy/kern/_src/linear.py
	GPy/models/ss_gplvm.py
improve numerical stability of vardtc_parallel
Merge branch 'devel' of github.com:SheffieldML/GPy into devel
recover the ss_gplvm.py
Noise parameters built depending on Y_metadata
Merge branch 'devel' of github.com:SheffieldML/GPy into devel
generalize the interface of mpi
Merge branch 'devel' of github.com:SheffieldML/GPy into devel
further bug fix for sparsegp_mpi
[normalizer] first commit for normalizer in GPy

Conflicts:
	GPy/core/sparse_gp.py
	GPy/models/bayesian_gplvm.py
[normalize]
[normalizer] only mean, because variance could be not Gaussian...